On tunneling to the center of the earth

Would it be possible to tunnel directly to the center of the earth using currently available means, or would the centrifugal effect cause you to unwittingly continue on toward the nearest point on the surface so that you emerge near the point where you began without ever having gone beyond a certain depth?

Whoa there people. I'm aware of the reality of the situation. :) Let's just assume that the earth is made of the same, solid material all the way through. But it is a rotating body, therefore wouldn't there be a centrifugal effect which prevents one from tunneling through to the center?

Staff: Mentor

When you used the phrase "currently available means" I assumed that meant you were asking a question about reality.... ok, then....

Let's just assume that the earth is made of the same, solid material all the way through. But it is a rotating body, therefore wouldn't there be a centrifugal effect which prevents one from tunneling through to the center?

No. Centrifugal force acts directly outward. You're probably thinking of the coriolis force. But I can't see why it would be a problem: drill bits can be steered.

I'm not sure if it would be the coriolis force, because that directs objects along a curved path. I'm referring to the force that directs an object that is sitting on a disc along a straight vector and outwards from the center when the disc is rotated at a certain speed. I'm aware that current drilling technology allows us to drill several miles below the earth's crust, but that may be due to the fact that the drill is situated on the surface. I'm also actually aware that centrifugal force is strongest near the edge of a rotating disc. I'm thinking that once you reach a certain depth, gravitational forces may be overcome by centrifugal forces.

My reason is this. The gravitational acceleration that we feel is caused by the curvature of spacetime due to the mass of the earth, but inside the earth there is no curvature because there is not enough of a difference in density. Therefore if gravity continues to an arbitrary point in the center, as GR says it does, then it would have to be a constant which neither increases nor decreases. Centrifugal force, however, increases linearly with distance from the center. So there should be a region in which gravitational acceleration is overpowered by the centrifugal effect.

Now there's probably something that prevents this centrifugal force from extending all the way to the surface, allowing us to penetrate several miles. One possibility is that gravitational acceleration is reduced but still not constant until that region is passed.

At the surface the centrifugal force is much weaker then gravity.
As you go deeper gravity will get weaker but so will the centrifugal force.
At the center both will be zero.
There is no point at wich the centrifugal force is stronger then gravity.

So the gravitational force is not reduced to a constant inside the earth but actually decreases with depth?

If the Earth had a uniform density the gravitational force inside the Earth would decrease linearly with depth, hitting zero at the center of the Earth. The Earth does not have a uniform density. The Earth's core represents only 16.3% of the Earth's volume but 32.5% of its mass. Rather than falling linearly with depth, gravity inside the Earth falls slightly and then starts rising, reaching a maximum at the mantle/core boundary. Only then does it start dropping precipitously toward zero at the center of the Earth.

If the Earth had a uniform density the gravitational force inside the Earth would decrease linearly with depth, hitting zero at the center of the Earth. The Earth does not have a uniform density. The Earth's core represents only 16.3% of the Earth's volume but 32.5% of its mass. Rather than falling linearly with depth, gravity inside the Earth falls slightly and then starts rising, reaching a maximum at the mantle/core boundary. Only then does it start dropping precipitously toward zero at the center of the Earth.